Underwater acoustic transducers employing polymeric piezoelectric film materials are known. In British patent No. 2,120,902, a shell of PVDF material is provided with the usual conductive coatings on each face thereof. When an alternating current of 100 cycles per second is applied to the coatings, the shell vibrates to act as an underwater sound generator.
In U.S. Pat. No. 2,939,970, a spherical microphone assembly includes spherical outer and inner electrodes with a spherical ceramic transducer element therebetween. The assembly may also be used as a loudspeaker. The spherical configuration of the microphone assembly is similar to the balloon shaped speaker of the present invention.
In U.S. Pat. No. 4,284,921, various configurations, including hemispherical, of thermoformed piezoelectric polymeric film materials are disclosed as transducer elements for purposes of receiving and transmitting.
The existing patented devices abovementioned do not suggest the present speaker which is light in weight, maneuverable, deflatable for easy storage and transport, and sufficiently inexpensive to permit its use at entertainment centers and celebrations where tables of guests, for example, could each have an individual balloon speaker with a preferred sound volume, and where the height of the inflatable balloon, filled with helium, for example, could be easily controlled. The electrodes or metallized film coatings of the piezoelectric polymeric film are connected to the output of an audio tape player, radio receiver, phonograph amplifier, and the like, each capable of delivering an adequate signal to energize the piezo film. Conventional amplification and impedance matching devices may be interposed between the audio device and piezoelectric film.
Additionally, the piezoelectric polymeric films of the present invention may function as a highly mobile and maneuverable microphone as well as sender/receiver of ultrasonic signals for communication, surveillance, and range finding purposes, when suitably attached and connected to an inflated balloon.